Most wiper arms of this type comprise a mounting part with an opening that is usually realized in the form of an inner cone. This opening extends coaxially with the drive shaft, on the end of which the wiper arm is then mounted. When mounting the wiper arm on the drive shaft, the opening of the mounting part is attached to the end of the drive shaft. The mounting part of the wiper arm is pressed onto the end of the drive shaft and rigidly fastened by screwing a separate fastening nut or separate fastening screw on or in the end of the drive shaft, with a washer being arranged between the mounting part and the fastening nut or fastening screw.
Wiper arms of this type are already known.
DE-GM 71 04 759 discloses a wiper arm with a mounting part that is realized in the form of a die-cast part and provided with an opening in the shape of an inner cone. The opening of the mounting part is attached to a knurled cone arranged on the end of a solid drive shaft and held by a separate fastening nut, with the fastening nut being screwed on the threaded stem of the drive shaft that extends through the opening in the mounting part in the form of an extension of the knurled cone. A covering cap of plastic covers the attached mounting part and the fastening nut.
DE 41 40 959 A1 discloses a different wiper arm in which the mounting part is realized in the form of a sheet metal body. A cast metal part that is provided with a conical opening for rigidly mounting the wiper arm on the conical end of a drive shaft is fastened to the aforementioned sheet metal part. This wiper arm is mounted on the drive shaft by attaching the mounting part onto the end of the drive shaft which is provided with an outer cone and a cylindrical threaded projection. A separate fastening nut is then attached. Consequently, the cast metal part of the mounting part is pressed onto the cone arranged on the end of the drive shaft and rigidly held thereon.
A wiper arm with a mounting part that is realized in the form of a die-cast part with a conical opening is known from DE 41 17 107 A1 or DE 41 34 980 A1. This wiper arm is fastened to the end of a drive shaft as described previously by utilizing a separate fastening nut. In this case, the drive shaft is realized in the form of a hollow shaft, with the hollow space of the drive shaft being used as a lead-through for the windshield-washing fluid. The mounting part and the fastening nut as well as the hose connection on the end of the drive shaft for conveying the windshield-washing fluid are covered with a covering cap after the wiper arm is mounted on the drive shaft.
All these known wiper arms are associated with the disadvantages described below.
When mounting the wiper arm on the drive shaft, a separate fastening nut must be screwed on the end of the drive shaft after the opening of the mounting part of the wiper arm is attached to the end of the drive shaft. This requires the additional transport and/or storage of fastening nuts as well as an increased mounting expenditure.
After a certain time, the wiper arm may require removal or replacement, e.g., if the windshield becomes damaged, the motor vehicle is repainted or the wiper arm is deformed due to excessive stress. However, the removal of the wiper arm is very complicated in most instances because the mounting part is very firmly seated on the drive shaft since it is pressed onto the end of the drive shaft. Once the fastening nut is unscrewed, the wiper arm can only be removed from the drive shaft with a very high expenditure of force. In this case, intact wiper arms are frequently bent or damaged such that they are rendered unusable and must be replaced. If unsuitable tools are used, the drive shaft or its bearings are frequently damaged, i.e., these components also must be replaced and the repair costs are significantly increased. Hollow drive shafts with lead-through for the windshield-washing fluid are particularly sensitive in this respect. If such drive shafts are damaged during the removal of the wiper arm, the repair costs are also increased.